JPS58131787A - Semiconductor laser - Google Patents

Abstract

PURPOSE:To obtain the semiconductor laser having a stable lateral oscillating mode with extremely excellent reproducibility and with high yield through only once epitaxial growth process by forming a semiconductor layer, an energy gap thereof is smaller than an active layer, onto a substrate in a concave shape at a deep groove section reaching the substrate and thickly growing the active layer onto the groove. CONSTITUTION:The striped groove 103 is formed to the semiconductor substrate 101 in approximately 1.5mum depth and 2mum width while penetrating a Zn diffusion layer 102 in parallel in the <011> direction through photolithography. An n-In0.66Ga0.34As0.74P0.26 layer 104 in 1mum thickness in a flat section, an n-InP buffer layer 105 in a shape that is 1mum thickness in a flat section and is slightly concave in the upper section of the groove 103, the nondoped In0.72Ga0.28As0.61 P0.39 active layer 106 in 0.15mum in the upper section of the groove 103 and 0.1mum in a flat section, a p-InP clad layer 107 in 2.5mum and a p-In0.85Ga0.15As0.33 P0.67 electrode layer 108 in 1mum are laminated in succession through a liquid epitaxial growth method.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a 2Jlk heterostructure semiconductor laser whose oscillation transverse mode is stabilized.

As the practical use of optical fiber communication progresses, stabilization of the transverse mode has become an essential condition for the semiconductor laser that is the light source. Rounding off the stabilization of the oscillation transverse mode Various laser structures have been proposed and prototyped, one of which is Mr. Imai's 1980 issue of Electronics Letters, Vol. 17, No. 1, pages 17 to 19. There is a &8ML laser reported by et al. This semiconductor laser is n-1
n)' 7 layers of n-1nP butts on the substrate, lnGaAm)
After laminating the active layer p-1nP cladding layer and n-n-1nGaA with the same emission wavelength as the active layer, the current injection part is etched in stripes up to the p-1n) cladding island, and the second With epitaxial g length, tll, 2(D
A p-1nP cladding layer and a p-1nGaAaP electrode layer are sequentially laminated. In this semiconductor laser, the FirnGaAm)' active layer and the n-1nGaAsP layer form a coupling waveguide in the direction perpendicular to the heterojunction in areas other than the stripe area, so light is transmitted between the stripe area and the other coupling waveguide areas. Due to the difference in the propagation constant, light can be concentrated only on the stripe portion, and therefore stable transverse fundamental mode oscillation can be obtained.

However, in Jin's case, two epitaxial growth steps were required to produce the confectionery, and the active layer, which had grown even further, was kept in a high-temperature atmosphere during the second crystal growth, making it susceptible to thermal damage. The object of the present invention is to eliminate the above-mentioned drawbacks, to stabilize the oscillation transverse mode, and to improve the manufacturing yield by making it possible to fabricate in a single epitaxial growth process. The object of the present invention is to provide a double hepatop structure half-fatty rape.

The structure of the semiconductor laser according to the present invention is a double heterostructure semiconductor laser having an active layer sandwiched between two semiconductor heterojunctions, and #! A second conductivity type semiconductor layer is formed on a semiconductor wafer in which an etching groove is formed through the second conductivity semiconductor layer. A first conductivity type half-layer, which is not large, is laminated, and on top of that, a first conductivity type half-layer, which has a large energy gap than the active layer, is laminated, and the active layer is etched on top of it. It is characterized by the fact that two rad layers of the second conductivity type, which have a large energy gap, are successively formed in the active layer and the active layer.

The present invention will be described below with reference to drawings showing embodiments.

Figure 1 shows a cross-sectional view of an embodiment of the present invention.
00)n-1n)' Zn, which is a p-type impurity, is diffused into the substrate 101 to a depth of 1 μm to form a Zn diffusion layer 102. This may be a p-1nP epitaxial growth layer with a thickness of about 1 μm or an ion implantation layer.
, is not limited to a Zn diffusion layer. On the semiconductor substrate, a stripe-shaped groove 103 is formed in parallel to the <011> direction to a depth of approximately 1.5 μm and a depth of @2 μm, using a conventional method of IJ SOGE 2 FI to penetrate the Zn diffusion layer 102. Form it like this. By using the lk liquid phase epitaxial growth method, firstly, n-1 nusGa with an emission wavelength composition of 1.4 μm was grown.
o14A@o, taPo, z@ pigeon 104 is then coated with n-1nP buffer layer 1 so that the thickness of the flat part is 1 μm.
05 to have a thickness of 1 μm at the flat part and a slightly concave shape at the top of tll103, and further 1.3 μm of emission wavelength composition (D/7-plno, tsGio, xsA g
o, *Po, s* The active layer 106 is set to 0.15 Am at the top of tll03 and α1jJm at the flat part, and the p-1nP cladding layer 107 is set to 54 m0 with an emission wavelength of 1.1
The crystal growth is completed by sequentially laminating ljlm of 6711 pole layers 108 on p-1nossGao, uAsass)' having a μm composition. At this time, n-1no, asOao, si A
8o, y4)'Ass layer 10 layers are grown thickly even on the flat part in 04 minutes, but it is not flat over the entire surface, and only the groove part has a concave shape, and as mentioned earlier. The n-In)' loose fluorine layer 105 is grown so as to have a slightly concave shape above the groove. When a positive bias is applied to the p-side of this semiconductor laser and a current is passed through it, the parts other than the striped $103 have a p-n-p-nm structure because of the Zn diffusion layer 102, and only the groove portion is formed. When the injection current is increased, the current effectively flows through the active layer 106.
The light-emitting region of tries to expand in the direction parallel to the p-n junction, but in areas other than the top of the
, t4Po, and the zs layer 104 are present nearby, so there is some loss for the light that permeates the Pacqua layer, and transverse higher-order modes cannot occur. As shown in 9@2Q, 1
nl-xGa XAI F )' 1- y-I n)
'Series DH-1. In D, the active layer thickness is 0.15 to 0.2
The oscillation threshold direct flow density is the minimum at μm (t), but if the thickness is thinner than that, especially 0.1 μm or less, the threshold direct flow density will increase rapidly, and at the same time, it will seep into areas other than the photoactive layer. This light trapping effect becomes even more significant as the light becomes larger. Therefore, even if the injection current is increased, only the transverse fundamental mode will stably exist in the range of 2 to 3 .mu.m above the surface. In this way, before crystal growth of the active layer, the Zn diffusion layer (or p-In)
By using a very narrow stripe-like layer that penetrates through the layer 102, a semiconductor laser with a stabilized transverse mode of oscillation can be produced by a single epitaxial growth process. It can be obtained with good reproducibility and the manufacturing yield is greatly improved. With this semiconductor laser cut to a cavity length of 250 μm, a device with an oscillation threshold current of 49 mA at room temperature and a differential quantum efficiency of about 50 factors can be produced with good reproducibility.

In the examples of the present invention, the emission wavelength of the active layer is set to 1.
3 μm, n-1nt-x (jazAiyPt-y layer 1040, 1.4 μm was selected as the emission wavelength composition, but 1Ht-xGaxAsyPl with a wavelength composition like Kono
-not limited to the y layer, n-1ns-xGaxAsy)
'1-y layer is a mesomorphic material whose energy gap is not larger than that of the active layer, and the chirality fL is good, and the Zn diffusion layer 1
02 is also formed by an epitaxial growth method or an ion implantation method to form a p-In)' layer or a p-Int layer.
-xGaxAay)'ty layer may be used. Furthermore, the semiconductor material used is Int-xGaxAay.
It is effective not only for Pl-y/1nP-based semiconductor materials but also for other semiconductor materials.

A feature of the present invention is that the active layer and the like are formed on the semiconductor substrate by using narrow striped grooves that are formed so as to pass through the Zn diffusion layer (or p-1nP layer) previously formed on the semiconductor substrate. Also, by making the semiconductor layer with a small energy gap concave in the groove part and growing the active layer thickly locally, the oscillation transverse mode is limited only to the upper part of the groove. A mode-stabilized semiconductor laser is produced through a single epitaxial growth process)
, obtained with extremely good reproducibility and high yield p.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view of the semiconductor laser of the example, and Fig. 2 is a cross-sectional view of the semiconductor laser of the example.
n)' is a diagram showing the relationship between the active layer thickness and the oscillation threshold perpendicular current density of a DH laser. In the figure, 101 ``'' n-1nP substrate, 102...
-Zfl diffusion layer or p-1nP layer, 103...
...St2 rib-shaped groove, 104 ...-n-1no
,s・Gao,m4AsataPo,***,105・
...n-In)' Barafu layer, 106...
・In O, 7mGa o, ssAs a・1po,
s*active layer, 107...p-1nP cladding layer, 10B...-p-1no, 5sGaa1s
AaO, 1lPO67 electrode layer, 109...P-type ohmic electrode, 110...N-type ohmic electrode 0 bar once

Claims (2)

[Claims] (1) In a 21-hetero Sakaki semi-dedicated laser with an active layer sandwiched between two semiconductor heterojunctions, the first
A wjJ2 conductive type semiconductor layer is formed on a conductive type semiconductor substrate, and an etched groove is formed on the semiconductor wafer in which an etched groove passing through the #&2 exclusive electric type asymmetrical layer is formed so that the height is the lowest at the etched groove part. , the active layer is also laminated with a first conductivity type half-conductor layer having a small energy gap, and a first conductivity type semiconductor clad layer having a larger energy gap than the # active layer is laminated thereon; A semiconductor laser characterized in that an active layer is formed thereon so as to be thickest at the upper part of the etching layer, and further a second low voltage type semiconductor cladding layer having a larger energy gap than the active layer is successively formed. (2) The semiconductor substrate and the semiconductor cladding layer are lnP, and the active layer is lnl-xQixλIFP.
I"F, the thickness of the active layer is 0.1 to α2 μm on the etched surface, and 0.1 μm on the flat part.
A semiconductor laser according to claim 1, characterized in that: